The physiologcal significance of the calcium transport in the erythrocyte membrane has been well documented. Several investigators have shown that the erythrocyte membrane(ghost) binds calcium. Others have shown that Ca-stimulated ATPase of the ghost is the manifestation of the Ca-transport activity. In sarcoplasmic reticulum, which is another calcium transport membrane system, calcium-stimulated ATPase as well as calcium binding proteins have been isolated and well studied. However, in erythrocyte membranes, solubilization and purification of such proteins haven't been done extensively. The present investigator was able to solubilize two different types of calcium binding proteins from human erythrocytes. The one seems to be muscle tropomyosin-troponin type regulatory protein, and the other, troponin-C type protein. In this proposed research, we will study the physicochemical properties as well as biochemical activities of these proteins. The physiological role of these proteins, such as their possible participation in the calcium transport and/or in the maintenance of mechano-chemical properties of the membrane will also be studied. In sickle cells, the calcium pump seems to be malfunctioning which results in higher calcium content of the cells and decrease of the deformability of the membrane. We will study whether there is any detectable abnormality in the quantity and/or the calcium-binding capacity of these proteins in the sickle cell.